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Temporal range:
Early Cambrian to Carboniferous
Hallucigenia sparsa.JPG
Hallucigenia sparsa
Scientific classification e
Kingdom: Animalia
Superphylum: Ecdysozoa
Phylum: "Lobopodia"
Class: Xenusia
Dzik & Krumbiegel, 1989[1]

See text.

Class Xenusia, the Xenusiids, represents the subset of lobopodian worms that fall in the stem-lineage of Onychophora.[2] Their type genus is Xenusion.[3] They have relatively large, annulated, cylindrical body. Their lobopod legs have tubercles at their bases. Some have large frontal appendages,[3] although these may represent taphonomic artefacts.[4] Their mouth is terminal or subterminal, and they are marine.[5] They probably represent a grade (paraphyletic group) rather than a clade (monophyletic group).


Xenusia includes the following orders and families:[5]

Order Archonychophora[edit]

These taxa are only known from the Chengjiang (Cambrian Stage 2 Series 3).

Order Protonychophora[edit]

  • Protonychophora Hutchinson, 1930 - Spiny legs, reduced tail
    • Aysheaiidae Walcott, 1911 - many claws on each leg. Anterior grasping appendages with long spines.
    • Xenusiidae Dzik & Krumbiegel, 1989 - >20 leg-bearing segments; paired, rounded sclerites on each segment; spiny legs.
      • Xenusion Pompeckj, 1927
      • Jianshanopodia Liu et al [3] - from Chengjiang; two rows of tubercles but no obvious sclerites
      • Hadranax Budd & Peel 1998 — from the Sirius Passet. Lacks obvious dorsal armature, but bears four 'nodes' per row.

Order Scleronychophora[edit]

  • Scleronychophora Hou & Bergstrom, 1995 - paired sclerites; elongated head sclerites
    • Eoconchariidae Hou & Shu, 1987 - ~10 leg-bearing segments, small head, sieve-like sclerites, varying in shape along body; curved claws on annulated legs; terminal mouth and anus.
    • Hallucigeniidae Conway Morris, 1977 - ~10 leg-bearing segments; large sclerites covering head; sclerites on each segment are long spines.
      • Hallucigenia Conway Morris 1977 - From the Chengjiang, Kaili and Burgess Shale[8]
    • Cardiodictyidae Hou & Bergstrom, 1995 - many segments (~23); large sclerites cover head; hexagonal sclerite on each body segment.

Order Paronychophora[edit]

  • Paronychophora Hou & Bergstrom, 1995 - short, downwards facing head; papillae on body and legs, some arranged in rows; shield-like sclerites on head; dorsal armature of spines;[9] claw-like jaws; annulated legs [ Note - diagnosis modified in [10] ]

Order unassigned[edit]

  • Orstenotubulus Maas et al 2007 from the Furongian Orsten deposits - with retractable dorsal spines[11]
  • Carbotubulus Haug et al 2012 [12] - from the Mazon creek. Dorwal armature uncertain. Few segments, long limbs.
  • Mureropodia,[13] from the Stage 2 Murero lagerstatten, Spain

'Phylum' Onychophora[edit]

Onychophora are distinguished by their terrestrial habit, their ventral mouth; their antennae, jaws and oral papillae; they seem to be most closely related to the Paronychophora. Their first fossils are Carboniferous (Helenodora), although they may have had a cryptic earlier history.


  1. ^ Dzik, J.; Krumbiegel, G. N. (1989). "The oldest 'onychophoran' Xenusion: A link connecting phyla?". Lethaia 22 (2): 169. doi:10.1111/j.1502-3931.1989.tb01679.x. 
  2. ^ a b Hou, X.; Bergström, J. A. N. (1995). "Cambrian lobopodians-ancestors of extant onychophorans?". Zoological Journal of the Linnean Society 114: 3. doi:10.1111/j.1096-3642.1995.tb00110.x. 
  3. ^ a b c Jianni Liu Degan Shu, Jian Han, Zhifei Zhang & Xingliang Zhang (2006). "A large xenusiid lobopod with complex appendages from the Lower Cambrian Chengjiang Lagerstätte" (PDF). Acta Palaeontologica Polonica 51 (2): 215–222. 
  4. ^ Julián Monge-Nájera & Xianguang Hou; Hou (2002). "Experimental taphonomy of velvet worms (Onychophora) and implications for the Cambrian "explosion, disparity and decimation" model" (PDF). Revista de Biología Tropical 50 (3–4): 1133–1138. PMID 12947596. 
  5. ^ a b George Poinar, Jr. (2000). "Fossil onychophorans from Dominican and Baltic amber: Tertiapatus dominicanus n.g., n.sp. (Tertiapatidae n.fam.) and Succinipatopsis balticus n.g., n.sp. (Succinipatopsidae n.fam.) with a proposed classification of the subphylum Onychophora". Invertebrate Biology 119 (1): 104–109. doi:10.1111/j.1744-7410.2000.tb00178.x. JSTOR 3227105. 
  6. ^ a b Ma, X.; Hou, X.; Bergström, J. (2009). "Morphology of Luolishania longicruris (Lower Cambrian, Chengjiang Lagerstätte, SW China) and the phylogenetic relationships within lobopodians". Arthropod Structure & Development 38 (4): 271. doi:10.1016/j.asd.2009.03.001. 
  7. ^ Xian-Guang Hou, Xiao-Ya Ma, Jie Zhao & Jan Bergström; Ma; Zhao; Bergström (2004). "The lobopodian Paucipodia inermis from the Lower Cambrian Chengjiang fauna, Yunnan, China". Lethaia 37 (3): 235–244. doi:10.1080/00241160410006555. 
  8. ^ a b Whittle, R. J.; Gabbott, S. E.; Aldridge, R. J.; Theron, J. (2009). "An Ordovician Lobopodian from the Soom Shale Lagerstätte, South Africa". Palaeontology 52 (3): 561–567. doi:10.1111/j.1475-4983.2009.00860.x. 
  9. ^ Liu, J.; Shu, D.; Han, J.; Zhang, Z.; Zhang, X. (2008). "The LobopodOnychodictyonfrom the Lower Cambrian Chengjiang Lagerstätte Revisited". Acta Palaeontologica Polonica 53 (2): 285. doi:10.4202/app.2008.0209. 
  10. ^ Ma, X.; Hou, X.; Bergström, J. (2009). "Morphology of Luolishania longicruris (Lower Cambrian, Chengjiang Lagerstätte, SW China) and the phylogenetic relationships within lobopodians". Arthropod Structure & Development 38 (4): 271. doi:10.1016/j.asd.2009.03.001. 
  11. ^ Maas, A.; Mayer, G.; Kristensen, R. M.; Waloszek, D. (2007). "A Cambrian micro-lobopodian and the evolution of arthropod locomotion and reproduction". Chinese Science Bulletin 52 (24): 3385. doi:10.1007/s11434-007-0515-3. 
  12. ^ Haug, J. T.; Mayer, G.; Haug, C.; Briggs, D. E. G. (2012). "A Carboniferous Non-Onychophoran Lobopodian Reveals Long-Term Survival of a Cambrian Morphotype". Current Biology. doi:10.1016/j.cub.2012.06.066. 
  13. ^ Gámez Vintaned, J. A.; Liñán, E.; Zhuravlev, A. (2011). "A New Early Cambrian Lobopod-Bearing Animal (Murero, Spain) and the Problem of the Ecdysozoan Early Diversification". Evolutionary Biology – Concepts, Biodiversity, Macroevolution and Genome Evolution. p. 193. doi:10.1007/978-3-642-20763-1_12. ISBN 978-3-642-20762-4.